1. Field of the Invention
The present invention relates generally to data cellular networks, and specifically to session management within data cellular networks.
2. Description of Related Art
High Rate Packet Data (HRPD) is a technology originally developed for dedicated packet data applications to meet the increasing demand for wireless Internet Protocol (IP) connectivity with high spectral efficiency. Voice transmissions require low data rates, but maintain stringent delay and jitter requirements. Packet data transmissions, on the other hand, typically require bursty high data rates, with less stringent delay and jitter requirements. The HRPD principle is to separate high-speed data completely from the voice network, so that the packet data requirements can be fulfilled optimally and independently.
In May 2000, the CDMA Development Group (CDG) accepted HRPD as the 1×Evaluation Phase One: Data Only (1×EV DO or 1×EV Phase 1), with minor requirements for improvements. Within the 1×EV DO cellular network, data-only (DO) mobile terminals, hereinafter referred to as Access Terminals (AT), utilize data services by initiating data sessions with data-only base stations, hereinafter referred to as Access Networks (AN). The AN's transmit and receive data packets to and from AT's over the air interface, and support packet data speeds above 144 kbps. It should be understood that the term AT as used herein refers to both DO terminals that utilize only data services and dual mode mobile terminals that are capable of utilizing both data services and voice services, but are currently operating in data mode.
To initiate a data session, an AT requests from a serving AN a Unicast Access Terminal Identifier (UATI) that uniquely identifies the AT within the serving AN. The UATI further includes an 8-bit field that identifies the Color Code of the AN within a Color Code Area or subnet. Each subnet includes up to 256 neighboring AN's that are allowed to transfer session information between each other. Upon receipt of the UATI, the AT engages in a session protocol negotiation process with the serving AN for the data session. The negotiated protocols and protocol configurations are stored within the AT and AN for later use in communications between the AT and the AN during the session. The UATI acts as a pointer to the session records within the AN.
After session configuration, the AT initiates Point-to-Point Protocol (PPP) and Link Control Protocol (LCP) negotiations for access authentication. Once authenticated, the data session begins with the AT in the dormant (i.e., idle) state. The AT can transition to the active state (e.g., engage in a packet data connection) at any time during the session. A session typically has a default duration of 54 hours. However, it should be understood that the session duration can vary depending upon the particular implementation.
Due to the extended session time, it is likely that a dormant AT may roam into another AN during the session. The new (target) AN uses the UATI Color Code to locate the original (source) AN. If the target AN is within the same subnet as the source AN, and the target AN is capable of supporting the session (e.g., protocol configurations are supported in the target AN), a dormant state handoff can be performed between the two ANs to transfer the session from the source AN to the target AN. Although the session protocol negotiation and terminal authentication operations do not need to be repeated during a dormant handoff, frequent dormant handoffs between AN's waste air link and network resources. In addition, the session transfer process could delay an active connection setup for the AT.
However, if the session is not supported in the target AN or if the target AN is located in a different subnet, the session must be re-negotiated over the air interface as if the original session never existed. For example, if an AT roams to a target AN that is not within the same subnet as the source AN, any attempted dormant handoff will fail since the correct source AN cannot be verified (i.e., the Color Code included in the previously assigned UATI is not recognized in the new subnet). Therefore, upon entering a new subnet, the AT must re-negotiate an entirely new session. The re-negotiation process causes additional delay and unnecessarily wastes air link and network resources. Therefore, what is needed is a session management procedure that enables seamless roaming between AN's.